DE19806837A1 - Thermoplastic resin for fluidised bed or electrostatic powder coating with high initial adhesion - Google Patents

Abstract

Resin material for powder coating comprises a thermoplastic resin powder of a polymer (I) with a heat of fusion \} 25 J/g, determined by differential calorimetry. Also claimed are powder coated articles with a metal surface coated with this powder. The heat of fusion is <= 10, especially <= 5 J/g. Suitable (I) are liquid crystal polymers, especially aromatic polyesters or polyester-amides, more especially with a melt viscosity (shear rate 1000/second) of 1-10000, especially 10-5000 P at a temperature 10 deg C above the melting point; and synthetic resins selected from polyethylene, polypropylene, polystyrene, polybutylene terephthalate, polyethylene terephthalate, polyamide resin, polycarbonate resin, acrylonitrile-butadiene-styrene (ABS) resin, polyarylene sulphide resin and copolymers or mixtures of these. The average particle diameter is 10-600 mu m. Powder coating is carried out by a fluidised bed immersion or electrostatic technique.

Description

The invention relates to a resin material for the Powder coating and a method for powder coating using the same.

In the powder coating methods of the prior art is known a vortex immersion method in which a metallic object to a temperature above the Melting point of a synthetic used for coating Resin powder heated, immersed in a fluidized bed and that synthetic resin powder melted and attached to the surface of the metallic object is glued. There is also a electrostatic coating process known in which a synthetic resin powder on the surface of a metallic Item attached and then heat treated in an oven becomes. A method is known in which a metallic Object that is at a temperature above the melting point of a synthetic resin powder used is heated, just covered with the resin powder.

The synthetic resin used includes any thermoplastic synthetic resin, which at a suitable Temperature melts, such as polyethylene, Polypropylene, polyvinyl chloride, polyamide, polyester and Polyphenyl sulfide. Each of these materials can be made specifically for the type of use can be selected.

Use the powder coating process shown above however, such problems arise that the appearance deteriorated and a long warming time of 40 minutes  or more is required to adhere to the metal achieve. No procedure has been found to address this To solve problems. Therefore, the present invention is the Task, a material for powder coating provide the disadvantages of the prior art does not have.

This object is achieved by the invention in the independent Claim 1 specified resin material for Powder coating, that specified in independent claim 10 Process for powder coating, as well as the independent Claim 13 specified article. Other advantageous details Aspects and refinements of the invention result from the dependent claims, the description and the Examples.

The inventors who dealt with these problems have done extensive research to get into a way a powder-coated object with a to create initial adhesiveness at which the adhesiveness is so good that it is against mechanical stress due to a Difference in the coefficient of thermal expansion between them and is protected from a substrate and has a good appearance having. You have found that a powder coated Object with the desired surface condition Execution of the invention can be achieved.

The invention relates in particular to a coated Item with good appearance, protected from mechanical load due to a difference in Coefficient of thermal expansion between the same and one Substrate, improved in heat resistance and adhesiveness.

The invention provides a resin material for powder coating, characterized in that a thermoplastic resin powder  has the heat of fusion of 25 J / g or less, which by Differential calorimetry is determined.

Preferred embodiments of the invention are as follows described in detail.

The thermoplastic resin powder for powder coating tion material of the invention includes any thermo plastic resin that has a heat of fusion of 25 J / g or less has, preferably 10 J / g or less, and more preferably 5 J / g or less, the heats of fusion by Differential calorimetry can be determined. For example, includes it is polyethylene, polypropylene, polystyrene Liquid crystal polymer, polybutylene terephthalate, Polyethylene terephthalate, polyamide resin, polycarbonate resin, ABS Resin, polyaryl sulfide resin and copolymers of these resins, des another powder of a thermoplastic elastomer, such as Example polyesters, polyamides, polyurethanes, polyolefins and Polystyrene. The thermoplastic resin powder of the invention can a mixture of two or more synthetic resins. A liquid crystal polymer and a polyalkylene terephthalate copolymer can be used, wherein the polyalkylene terephthalate copolymer as the main ingredient Polyalkylene terephthalate with 2 to 4 carbon atoms per Alkylene unit and 1 to 40 mole percent of another comonomer Unit contains. In particular, the liquid crystal polymer from the standpoint of heat resistance, the Coefficient of linear expansion and surface hardness prefers.

The liquid crystal used in the present invention stall polymer has a molecular one in the molten state Alignment and shows an optical anisotropy. The Anisotropy in a molten state can result from conventional methods for checking polarization under  Using an orthogonal polarizer. In particular, an anisotropic melted phase can occur Observation of a molten sample under a Nitrogen atmosphere is placed on a Leitz heating table, using a Leitz polarizing microscope at a 40 times magnification can be confirmed. The polymer of the present invention transmits polarized dense even in a molten, steady state when it is between orthogonal polarizers is checked, and shows a optical anisotropy. This can be done through an optical pattern can be observed, which for a liquid crystal phase in is characteristic of a certain temperature range if the polymer is gradually heated. Can also by X-ray diffraction is peculiar to the phase Diffraction patterns can be observed. In general, the thermal analysis using a differential scanning calorimeter used, and a change in entropy and Transition temperatures at different phase transitions can be measured.

For the liquid crystal polymer, aromatic polyesters and aromatic polyester amides preferred. There is also a Polyester, the partially aromatic polyester and aroma contains table polyesteramide in the same molecular chain preferred example.

Aromatic polyesters in particular are used as liquid crystals and aromatic polyester amides preferred, each as Structural component at least one connection selected from the group consisting of aromatic hydroxycarboxylic acids, aromatic hydroxylamines and aromatic diamines, contain.

In particular, this includes ver applied liquid crystal polymer:  

• 1) Polyester comprising primarily at least one aromatic hydrocarboxylic acid or a derivative thereof,
• 2) Polyester comprising primarily:
• a) at least one aromatic hydrocarboxylic acid or Derivative thereof;
• b) at least one aromatic dicarboxylic acid, alicyclic dicarboxylic acid or a derivative thereof, and
• c) at least one aromatic diol, alicyclic diol or a derivative thereof,
• 3) polyester amide primarily comprising:
• a) at least one aromatic hydrocarboxylic acid or Derivative thereof
• b) at least one aromatic hydroxylamine, aroma table diamine or a derivative thereof, and
• c) at least one aromatic dicarboxylic acid, alicyclic dicarboxylic acid or a derivative thereof, and
• 4) polyester amide primarily comprising:
• a) at least one aromatic hydrocarboxylic acid or Derivative thereof
• b) at least one aromatic hydroxylamine, aroma table diamine or a derivative thereof,
• c) at least one aromatic dicarboxylic acid, alicyclic dicarboxylic acid or a derivative thereof, and
• d) at least one aromatic diol, alicyclic diol or a derivative thereof.

Furthermore, if necessary, a means of controlling the Molecular weight in combination with those described above structural components are used.

Preferred examples of certain compounds that make up the liquid crystal polyester of the present invention composed of naphthalene compounds such as Example 2,6-naphthalene carboxylic acid, 2,6-dihydroxynaphthalene,  1,4-dihydroxynaphthalene and 6-hydroxy-2-naphthylic acid, Biphenyl compounds such as 4,4'- Diphenyldicarboxylic acid and 4,4'-dihydroxybiphenyl, in para Position substituted benzene compounds and multiply substi tuated benzene compounds thereof (substituents are made Chlorine, bromine, methyl, phenyl and 1-phenylethyl selected), such as for example p-hydroxybenzoic acid, terephthalic acid, Hydroquinone, p-aminophenol and p-phenyldiamine, and meta- Position substituted benzene compounds such as Isophthalic acid and resorcinol.

Preferred examples of the specific compounds include naphthalene compounds such as 2,6-naphthalenedicarboxylic acid, 2,6-dihydroxynaphthalene, 1,4-dihydroxy naphthalene and 6-hydroxy-2-naphthylic acid, biphenyl compounds such as 4,4'-diphenyldicarboxylic acid and 4,4'-dihydroxybiphenyl, and a compound represented by the following formula (I), (II) or (III):

(where X represents a group selected from alkylene (C ₁ to C ₄ ), alkylidene, -O-, -SO-, -SO ₂ -, -S- and -CO-, Y represents a group selected from - (CH ₂ ) _n - (n = 1 to 4) and -O (CH ₂ ) _n O- (n = 1 to 4) represents).

Furthermore, the liquid crystal polyester of the present Invention in addition to the structural described above Components partially without polyalkylene terephthalate anisotropic melt phase in the same molecular chain contain. In this case the alkyl group has 2 to 4 Carbon atoms.

A more preferred example is a polyester that acts as a important structural component at least one connection, selected from the naphthalene compounds, the Biphenyl compounds and those substituted in the para position Benzene compounds from the structural described above Contains components. Among those substituted in the para position Benzene compounds are particularly important preferred examples around p-hydroxybenzoic acid, methylhydroquinone and 1-phenylethyl hydroquinone.

Specific examples of the compounds having an ester bond as contain functional group, which is the struktu real components, and special examples of Polyesters that form an anisotropic melt phase, which preferably used in the present invention are described in JP-B-63-36633.

In general, the aromatic ones described above show Polyester and polyester amide preferably an inherent Viscosity (I.V.) of at least about 2.0 dl / g, for example about 2.0 to 10.0 dl / g when in parafluorophenol in a Concentration of 0.1 percent by weight dissolved at 60 ° C will.  

That to be preferably used in the invention Polyalkylene terephthalate copolymer is a copolymer that is known as Main component is a polyalkylene terephthalate with 2 to 4 Carbon atoms in the alkylene unit and 1 to 40 mole percent another comonomer unit. In particular it is about the main ingredient is a polyalkylene terephthalate, that by polycondensation of terephthalic acid or one ester-forming compound and an alkylene glycol with 2 to 4 Carbon atoms or an ester-forming compound, such as Example polyethylene terephthalate, polybutylene terephthalate and Polypropylene terephthalate. 1 to 40 mole percent Another comonomer unit consists of, for example Dicarboxylic acid or an ester-forming compound, such as Example isophthalic acid, adipic acid, sebacic acid, dodecane Diacid and naphthalene dicarboxylic acid, or a di- Relatively low molecular weight hydroxy compound or an ester-forming compound, unlike the glycol unit the main component, such as ethylene glycol, 1,3- Propanediol, 1,4-butanediol, neopentyl glycol and hydroquinone.

If the heat of fusion determined by differential calorimetry is greater than 25 J / g, the synthetic resin powder melts heavy in contact with the surface of the heated Metal surface. It also happens when that synthetic resin powder is great, causing problems, so Surface of the coating can become rough and gas bubbles can arise. If the heat of fusion is 25 J / g or less it melts with less heat and the problem mentioned above does not arise.

It is preferred that the synthetic resin powder have a Has melt viscosity of 1 to 10,000 poise and esp special 10 to 5000 poise, at a temperature around 10 ° C is higher than the melting temperature thereof, at one Shear rate of 1000 / sec. If the melt viscosity  is less than 1 poise, the synthetic resin has a too great fluidity, and this undesirably results that the film drips and has an uneven thickness. When the melt viscosity is greater than 10,000 poise it has poor fluidity and an uneven flow Coating thickness, and finally it has to be renewed Heating can be smoothed. In any case, it is difficult to produce a coating with a good appearance.

The synthetic resin powder of the invention is not special limited to an average size. From the standpoint of Appearance it preferably has a through Cutting size from 10 to 600 microns, especially 20 to 400 µm.

The resin material of the invention can be mixed with one as needed inorganic filler in the form of fibrous, powdered, plate-like and hollow substances are mixed.

For example, the fibrous filler is an inorganic fibrous substance, including glass fiber, Silica fiber, silica aluminum fiber, zirconia fiber, Boron nitride fiber, silicon nitride fiber, carbon fiber, boron fiber, Potassium titanate fiber and then a metal fiber such as for example stainless steel, aluminum, titanium, copper and brass.

Then the powder filler includes carbon black, graphite, silica, quartz powder, Glass beads, ground glass fiber, glass powder, calcium silicate, Aluminum silicate, kaolin, talc, clay, diatomaceous earth, Silicates such as wollastonite, iron oxides, titanium oxides, Zinc oxides, oxides of a metal such as aluminum, Metal carbonates such as calcium carbonate and Magnesium carbonate, metal sulfates, such as Calcium sulfate and barium sulfate, and then ferrites, Silicon carbide, silicon nitride, boron nitride and metal powder.  

Then the plate filler includes mica, glass flakes and Metal foils. The hollow filler includes siras balloon and glass balloon.

The inorganic fillers can be one, two or more Types can be used in combination with each other. The ink pen can be used together with a conventional surfactant can be used to achieve the intended purpose. The For example, surfactants include functional ones Compounds, such as epoxy compounds, Isocyanate compounds, titanate compounds and Silane compounds.

Conventional can also be used within the scope of the present invention Additives are added, such as anti Oxidizing agents, thermal stabilizers, ultraviolet absorbers, Lubricants, mold release agents, colorants, such as Dyes and pigments, antistatic agents, surface-active Fabrics, flame retardants, flame retardant additives and heat-resistant organic filler.

Examples

The invention will now be described in more detail with reference to the games described, although the invention is not based thereon is limited.

Tests are carried out as follows.

(1) melting point (Tm) of the thermoplastic resin powder and Amount of heat of fusion (Δ Hm)

The determination was made with a differential scanning ka lorimeter DSC-7 from Perkin Elmer Co., Ltd. Of the  Melting point (Tm) was determined by heating a sample with a Temperature increase speed of 10 ° C / min. and measurement of Peak temperature determined in an endothermic curve occurred due to melting. The amount of heat of fusion (Δ Hm) was calculated from the endothermic curve due to the Melting determined using indium as a reference.

(2) Melt viscosity

The melt viscosity was at a shear stress of 1000 / sec at a temperature that was 10 ° C higher than that Melting point of the thermoplastic resin powder, with Capilograph (Brand name) determined by Toyo Seiki Co., Ltd.

(3) smoothness

The smoothness of the coating was rated with the following two characters:
○: good
X: bad

(4) Adhesion 1 of the coating

This was done according to the cross-cut test of JIS-K 5400 certainly. No flaking is marked with "○" and where a Chipping occurred, this is referred to as "X".

(5) Adhesion 2 of the coating

A heat resistance test was carried out in an oven at 200 ° C 100 hours. The adhesion of the coating was tested according to the JIS-K 5400 cross cut test. No flaking is indicated with "○", and where flaking occurred, this is referred to as "X".  

Examples 1 to 2

There were thermoplastic resin powders with the in Table 1 specified type of resin and an average size produced. They were dried at 150 ° C for 2 hours. The resin powders were electrostatically on steel plates applied and in an oven at 340 ° C for 20 minutes warms to get powder coated items. Table 2 shows the results.

Comparative Example 1

Polyphenylsulphide (PPS) powder was as shown in Table 1 made with an average size and at 2 hours 150 ° C dried. The resin powders became electrostatic Steel plates applied and baked in an oven for 2 hours Heated 340 ° C to obtain powder coated items. Table 2 shows the results.

Comparative Example 2

Polybutylene terephthalate (PBT) powder was as in Table 1 shown made with an average size and 2 hours dried long at 150 ° C. The resin powder was mixed with a Whirling process on the surface of steel plates applied, previously heated at 400 ° C for 10 minutes to get powder coated items. table 2 shows the results.

Example 3

The same resin powder that was used in Example 1 was applied to the surface of Steel plates applied previously at 400 ° C for 10 minutes  were heated to obtain powder coated articles. Table 2 shows the results.

The liquid crystal polyesters used in the example are shown below.

(The numbers above are based on molar ratios)  

Table 1

Table 2

Claims (13)

1. Resin material for powder coating, characterized in that it is a thermoplastic resin powder with a heat of fusion of the polymer determined by differential calorimetry of not more than 25 J / g. 2. resin material for powder coating according to claim 1, the heat of fusion of the polymer being 10 J / g or less is. 3. resin material for powder coating according to claim 2, the heat of fusion of the polymer being 5 J / g or less is. 4. Resin material for powder coating according to one of the Claims 1 to 3, wherein it is the thermoplastic Resin is a liquid crystal polymer. 5. resin material for powder coating according to claim 4, wherein the liquid crystal polymer is selected from the Group consisting of aromatic polyesters and aromatic polyester amides. 6. Resin material for powder coating according to one of the Claims 1 to 5, which has a melt viscosity (Shear rate: 1000 / sec.), Determined at one um 10 ° C higher temperature than the melting point of the thermoplastic resin, from 1 to 10,000 poise.   7. resin material for powder coating according to claim 6, which has a melt viscosity of 10 to 5000 poise having. 8. Resin material for powder coating according to one of the Claims 1-7, wherein the thermoplastic resin powder average particle diameter from 10 to 600 µm having. 9. Resin material for powder coating according to one of the Claims 1 to 8, wherein the synthetic resin is selected is from the group consisting of polyethylene, Polypropylene, polystyrene, polybutylene terephthalate, Polyethylene terephthalate, polyamide resin, polycarbonate resin, ABS resin, polyaryl sulfide resin and copolymers of these resins or mixtures thereof. 10. Process for powder coating, using a resin material for powder coating according to one of claims 1 to 9 is used. 11. A method for powder coating according to claim 10, wherein it is a swirl immersion process. 12. A method for powder coating according to claim 10, wherein it is an electrostatic coating process acts. 13. Powder coated article made by Be layering the surface of a metal with a thermoplastic resin powder according to any one of claims 1 till 9.